I'm running two half size supers for honey - two weeks ago I took 4 full frames off the top and left 3 that were capped fully on one side but only half capped on the other - I turned these around and brought some part filled up from the second box and added stickies to the second box.

A week later all 20 frames are completely full but only half capped from the top down even the sides that were fully capped are now half capped. I added another box of stickies under them and left them for other week to see what happens.

At a guess they are on a bit of a flow and are uncapping in order to extend the comb out further. It's good if they uncap to do this - I've had some frames with 2 layers of cappings.

Or perhaps they are using the ripe honey for feeding purposes.

Whatever is happening, it is best to have 80-100 % capped for extraction. They will cap when they are ready and the way your hives are filling up, it sounds like you might have to dust off some honey jars.

I have also noticed in a big flow that they capping won't be done till the flow starts to ease up a bit. In this case it is handy to add supers as you have done.

We were shown a technique on the beek course to determine if honey is ready to harvest if uncapped.

Take your frame - knock/brush the bees off the hold the frame horizontal with a face down - give the frame one sudden sharp downward shake - if any liquid showers to the ground it is not ready - if nothing comes out you can harvest.